1. Field of the Invention
This invention relates to the field of post-foaming compositions, more particularly to post-foaming shaving gels, and still more particularly to a post-foaming shaving gel including (a) a surfactant system, (b) the polymers poly(ethylene oxide) and polyvinylpyrrolidone, preferably in a weight ratio falling within a specified range, and (c) a post-foaming agent.
2. Description of the Related Art
Post-foaming shaving gels, also known as "self-foaming" or just "foaming" shaving gels, have become popular because of their unique characteristics: in use, the product is dispensed from a container in a gel form substantially free from foam, and is transformed into a foam when rubbed onto the skin. (In this respect, post-foaming shaving gels differ from "shaving creams", which are dispensed as foam.) To effect the transformation from gel to foam, a post-foaming agent comprising a hydrocarbon propellant is typically provided in the post-foaming shaving gel. The post-foaming agent volatilizes when the post-foaming shaving gel is rubbed onto the skin, thereby changing the post-foaming shaving gel into a foamy lather.
In addition to the post-foaming agent, other ingredients of known post-foaming shaving gels have included, for example, surfactants for cleaning (including soaps and synthetic detergents), gellants (also known as gelling aids) or thickeners, agents for adjusting lubricity, water, humectants, emollients, fragrances, and colorants.
As for gellants, thickeners, and agents for adding lubricity, in particular, a variety of ingredients have been mentioned in the related art. For example, U.S. Pat. No. 5,451,396 (commonly assigned to the assignee of the present application) to Villars lists as preferred gelling aids "water-soluble hydroxyalkyl cellulose or naturally derived gums such as xanthan, various synthesized polymers such as polyvinyl pyrrolidone, as well as chemical or enzymatically modified derivatives of these materials." U.S. Pat. No. 5,326,556 to Barnet, et al. refers to polyethylene oxide and hydroxyethyl cellulose as preferred water-soluble polymers. U.S. Pat. No. 5,560,859 to Hartmann, et al. discusses use of poly(ethylene oxide) as a gel stabilizer.
Several of the aforementioned compounds are found in a series of conventional shaving gels (referred to as the 14614D series) manufactured by S. C. Johnson & Son, Inc., the assignee of the present application. Each of those gels includes, among other ingredients, (a) poly(ethylene oxide) (POLYOX.RTM. WSR 301), (b) hydroxyethyl cellulose, (c) a soap with stearic acid, palmitic acid, and triethanolamine, and (d) a post-foaming agent with either (i) isopentane and isobutane or (ii) n-pentane and isobutane. These gels, hereinafter, collectively will be referred to as the "conventional S. C. Johnson shaving gel."
However, conventional post-foaming shaving gels, such as the conventional S. C. Johnson shaving gel, leave room for improvement in a number of respects. Consider, for example, the conventional S. C. Johnson shaving gel. That shaving gel is an excellent shaving composition; nonetheless, a number of areas for improvement were noticed, both in manufacturing and in use. In the manufacturing process, the ingredients which comprise the shaving gel were mixed together, and the resulting, substantially liquid mixture was filled into an open, unpressurized container (such as, for example, an aerosol can), which was then pressurized and capped. To convert the substantially liquid mixture to gel form, it was necessary to let the container rest at about room temperature for about two weeks. In some cases, it was necessary to heat the container to about 130.degree. F. for about two to three hours to provide energy sufficient to effect the conversion to gel form. Not only was the conversion from liquid to gel form difficult, but another disadvantage was present in the manufacturing process: when the substantially liquid mixture was dispensed into the open, unpressurized container, it tended to foam rapidly if post-foaming agents having a high vapor pressure were used, or if large amounts of high or low vapor pressure post-foaming agents were used. Of course, such foaming was unacceptable because the product was intended to be a substantially foam-free gel. As a result, it was necessary to use post-foaming agents having a lower vapor pressure, or to reduce the total amount of post-foaming agents, so as to obviate the foaming problem. However, both of these solutions were disadvantageous because, when the resulting shaving gel was used, it produced a foam which was denser, heavier, and less commercially desirable than that produced by shaving gels incorporating higher-vapor pressure post-foaming agents or a greater total amount of post-foaming agents.
In addition to these manufacturing problems, a number of disadvantages arose with the conventional S. C. Johnson post-foaming shaving gel when used. For example, the characteristics of the post-foaming shaving gel were such that it was not as easy as desired to rinse the foam produced by the post-foaming shaving gel from the skin. In addition, although the post-foaming shaving gel remained in a substantially foam-free form for a number of minutes upon being dispensed, it was commercially desirable to increase this amount of time.
I believe that other commercially available post-foaming shaving gels have the same or similar disadvantages, in manufacture or use.
Accordingly, a need has arisen to overcome drawbacks associated with conventional post-foaming shaving gels, such as those discussed above, and to provide a composition, such as a post-foaming shaving gel, for example, having improved properties.